Proteins for Immunoassays

Streptavidin

Streptavidin is a biotin-binding protein purified from the bacterium Streptomyces avidinii. The protein can be conjugated to enzymes, enabling detection of biotinylated antibodies and probes in a variety of standard assay methods such as ELISA and Western blotting.

Protein A

Protein A is a surface protein originally obtained from the cell wall of Staphylococcus aureus. It binds with high affinity to IgG of several species including human and rabbit. However, there are variations in interactions within species, eg. it will bind to human IgG1, IgG2 and IgG4 but not to IgG3. Protein A can be used to probe and detect human and rabbit antibodies in ELISA, Western blotting and other immunoassay protocols.

Protein G

Protein G is an immunoglobulin-binding protein isolated from group G Streptococcal bacteria. It is similar in function to Protein A, but offers a greater affinity for most mammalian IgGs. Protein G can be used to probe and detect human and mouse antibodies in ELISA, Western blotting and other immunoassay protocols.